Reliable stereo imaging requires the two speakers and the listener to form an equilateral triangle

To judge stereo balance and panning reliably, place the monitors so the distance between the two speakers equals the distance from each speaker to the listener’s head — an equilateral triangle aimed at the sweet spot, where both speakers blend, at or just behind the listening position. This follows from precedence: the brain localises a sound toward whichever ear it reaches first, so once the listener drifts off the centreline the whole image folds toward the nearer speaker. Speakers placed too close smear the stereo field; placed too far apart they collapse the phantom centre — where the most important sounds (lead vocal, kick, snare, bass) usually sit — and push the sweet spot too far back. Err toward slightly-too-close rather than too-wide, since a narrow image is easier to mix on than an unstable centre. Refinements: keep the room roughly symmetrical around the line of sight so reflections don’t unbalance the image; set tweeters to ear height, angled toward or slightly past the listener; and decouple monitors from the desk (neoprene pads, isolation stands) to reduce comb filtering from sympathetic resonance.

Examples

Sit 1.4m from the monitors and start with them 1.4m apart. If they are 2m apart while you sit 1.2m from each, the phantom centre collapses and the lead vocal seems to jump toward one side. A commonly cited console optimum is ~67.5 inches tweeter-to-tweeter; decoupling pads or isolation stands eliminate low-frequency phase cancellation from desk resonance.

Assessment

Set up a pair of monitors for a listening position 1.2m away: give the correct speaker separation, tweeter height/angle, and one method to decouple them from the desk. Then diagnose a setup with speakers 2m apart and a listener 1.2m from each — what is wrong, what will it do to your stereo-balance judgments, and which way should you err if unsure of spacing?